C/1906 E1 Kopff
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Comet C/1906 E1 was discovered on 4 March 1906, 4.5 months after perihelion passage, and was last seen on 4 July 1907 [Kronk, Cometography: Volume 3].Soon, the comet was found on two photographic plates exposed on 15 January 1905 and 10 January 1904 in Königstuhl Observatory (Heidelberg).
This comet made its closest approach to the Earth on 2 March 1906 (2.60 au), that is two days before its discovery.
E.E. Barnard (Yerkes Observatory) observed secondary faint component (3-4 magnitudes fainter than the principal nucleus) between the period of 1906 March 17 – 1906 March 31 (AJ 1908, Vol. 25, 83). At that time, the comet was at a distance of about 3.6 au from the Sun and 2.6 au from the Earth and just five months after perihelion passage.
Two solutions given here are based on data spanning over 3.48 yr in a range of heliocentric distances from 6.53 au through perihelion (3.34 au) to 6.38 au; however the preferred orbit is based on shorter arc of 2.18 yr including data only before the detection of secondary component.
This Oort spike comet suffers moderate planetary perturbations during its passage through the planetary system that lead to escape the comet from the solar system on a hyperbolic orbit (see future barycentric orbit).

C/1906 E1 is included to the list of split comets for unknown reasons in Comets II.

solution description
number of observations 97
data interval 1904 01 10 – 1906 03 16
data arc selection data generally limited to pre-perihelion (PRE)
range of heliocentric distances 6.53 au – 3.35 au (perihelion) – 3.62 au
detectability of NG effects in the comet's motion comet with determinable NG~orbit
type of model of motion GR - gravitational orbit
data weighting YES
number of residuals 166
RMS [arcseconds] 1.80
orbit quality class 1b
orbital elements (heliocentric ecliptic J2000)
Epoch 1905 10 02
perihelion date 1905 10 18.51416710 ± 0.03924524
perihelion distance [au] 3.33875628 ± 0.00016725
eccentricity 0.99960249 ± 0.00026474
argument of perihelion [°] 158.645341 ± 0.007050
ascending node [°] 343.623636 ± 0.000900
inclination [°] 4.282124 ± 0.000316
recip semi-major axis [10-6 au-1] 119.06 ± 79.30
Upper panel: Time distribution of positional observations with corresponding heliocentric (red curve) and geocentric (green curve) distance at which they were taken. The horizontal dotted line shows the perihelion distance for a given comet whereas vertical dotted line - the moment of perihelion passage.
Lower panel (panels): O-C diagram for this(two) solution (solutions) given in this database, where residuals in right ascension are shown using magenta dots and in declination by blue open circles.